For several decades, the incidence of allergic diseases has been on the increase in industrialized countries. Thus, it is nowadays estimated that 20% of the population of developed countries is affected by a form of allergy such as asthma, atopic dermatitis, or other forms of manifestations. This high incidence today places allergy as a public health problem and hence numerous research studies have been undertaken in order to try to provide solutions which make it possible to limit the development of these pathologies. These research studies have made it possible to identify the first 2 years of life as a critical period in the establishment of the disease, and in particular by phases for sensitization to allergens, children developing sensitization during this period being at a greater risk of subsequently developing an allergy. Moreover, the role of the intestinal flora in the onset of the allergy has also started to be revealed. Indeed, the establishment of the intestinal flora in children determines the development of the mucosal immune system (Prescott et al., 2005), and the modes of establishment of the flora could influence the immune orientation toward oral orientation or on the contrary toward sensitization (Kalliomaki et al., 2001; Sudo et al., 1997).
Allergy is defined more precisely as a hypersensitivity reaction involving an immune mechanism (Johansson et al., 2001). This hypersensitivity causes reproducible symptoms, triggered by exposure to an antigen, at a dose that is normally tolerated in normal subjects. The antigens causing an allergic reaction, the allergens, are very diverse in nature, of the food, air or animal type, and the like. Likewise, the symptoms observed vary widely, and are mainly of the skin, digestive or respiratory type. The strategies proposed for preventing the allergy have the objective of reducing the incidence of new cases of allergy (primary prevention), or of limiting the duration and the progression of the allergy when it is established (secondary prevention).
In infants, the most frequent allergies are food allergies, and in particular cow's milk protein allergy (CMPA). This risk is all the more great in atopic subjects (high allergic risk children, in particular due to a known allergic heredity), which justifies a strategy, in these children, of dietary intervention during early childhood. Prolonged (>6 months) exclusive maternal breastfeeding, combined with gradual dietary diversification, is the reference solution, breastfeeding having a potentially protective effect toward the appearance of an allergic disease (Host and Halken, 2005). For at-risk children who don't have the advantage of maternal breastfeeding, another strategy involving denaturation of cow's milk proteins by partial or extensive hydrolysis, or their replacement with other animal or plant proteins, is recommended (Host et al., 1999). Yet, the preventive efficacy of these solutions remains controversial (Osborn and Sinn, 2006a; Osborn and Sinn, 2006b), and the hydrolysis process has the consequence of damaging the organoleptic quality and the nutritional quality of the proteins, causing refusal in some children. In France, the hydrolyzed formulas are furthermore subject to specific legislation limiting their distribution to the pharmacy network exclusively, which is an additional constraint for parents of these at-risk children.
The anti-allergenic effect of fermented milks has been described, from a mechanistic angle, by Peng et al. The products studied are acidified probiotic fermented milks (pH=3.7) of the “yogurt” type. In the model presented, the effect is due to the double component of the product tested: fermentation and keeping the ferments alive (>109 cfu/ml). Five different types of ferments were tested (3 lactobacilli, 1 Streptococcus thermophilus MC and 1 Bifidobacterium longum) and the authors observed widely varying effects dependent on the strain used. In this animal model, the most remarkable effects were observed for the strains of lactobacilli tested. Moreover, the effects observed are purely of the immunological type, and not directly linked to clinical observations on the symptomatology of the allergic type (Peng et al., 2007). It should be noted, moreover, that all probiotic strains are not compatible with infant nutrition, D-lactic acid being nonmetabolizable by breastfeeding infants.
Terpend et al. studied more specifically the properties of a milk fermented by Bifidobacterium breve and Streptococcus thermophilus. The results of this study show an effect of strengthening of the intestinal barrier against milk proteins. However, these authors failed to demonstrate a direct antiallergenic effect of such a fermented milk (Terpend et al., 1999).
In this context, the inventors have developed formulations suitable for infant nutrition, which at least partially overcome the disadvantages of the products described in the prior art, which makes it possible to provide a different approach in the dietary management of children having an allergic risk.